Many beverage providers, such as bars, sell a number of different beverages. Often, each of these beverages will be stored in a beverage dispenser that includes a container, such as a keg, and a dispensing mechanism, such as a tap. When a customer orders a quantity of the beverage (e.g., a pint of beer), an employee (e.g., a bartender) of the beverage provider will pour the beverage (e.g., dispense the beverage from a tap into a glass) for the customer. After pouring the beverage, the bartender will usually charge the customer for the beverage and, in most cases, the customer will pay for the beverage.
Typically, the bartender determines that a container of the beverage is empty when the dispensing mechanism stops dispensing the beverage. At this point, the bartender can replace the container with a new container, if one is available.